Email templates and their customization

[rkmax]

it's pretty common to send emails on different situations

• welcome after signup or email confirmation
• email confirmation
• when a forgot password process start
• when a forgot password process ends

and add the following configuration options that allows authentication module users to customize his needs.

• ENV to decide if confirmation email is needed or not
• ENV to pick a path for custom templates

custom templates should only replace those that are present in that way facilitate the use of the module without the need to customize all templates